The Histology and Immunohistochemistry Core will evaluate tissues from mutant and wild type mice for projects 2, 3 and 4. The purpose will be to assess any histochemical or cellular abnormalities at the light micrographic level. Bone, cartilage and other tissues will be surveyed by routine histological techniques, as well as by immunofluorescent approaches for matrix molecules including the collagen types, osteopontin, osteocalcin and alkaline phosphatase. Comparisons will be made between normal tissues and those eliciting gross or microanatomical variations. Since the targeted genes focus upon bone and cartilage macromolecules, the histological evaluations will also focus upon bone, cartilage and surrounding tissues. Nevertheless, routine surveys of other tissues will also be made. The core will also provide appropriate micrographs and slides for publication and presentation. Since evaluation of defects brought about by genetic manipulations described in this proposal at the microanatomical level are vital, the Histology and Immunohistochemistry Core is an essential part of this program.